Magnetic memory storage device

ABSTRACT

A storage device including a magnetic memory and a control circuit. The control circuit is configured to transfer selected data from the magnetic memory a selected number of times and to regulate the transfer of the selected data from the magnetic memory subsequent to transferring the selected data from the magnetic memory the selected number of times.

BACKGROUND OF THE INVENTION

Non-volatile storage devices are used to store a variety of types ofmaterial. For example, CD's and DVD's store material such as movies,music, books and software programs. In these applications, the CD's andDVD's are typically programmed at a manufacturing facility anddistributed to intermediaries for distribution to consumers. Theintermediaries, such as retail stores and video rental stores, selland/or rent the programmed devices to the consumer for home use.

Consumers forego the cost of buying a CD or DVD by renting it from arental store at a lower fee. In rental situations, the burden is placedon the consumer to go to the rental store to pick up the device, whichmust be done during the store's regular business hours. Also, theconsumer must return the rented device to the rental store within a setnumber of days to avoid paying a late fee.

The intermediaries and producers of the material stored on the CD's andDVD's maintain control over distribution of the material by charging alate fee. The late fee can be as much or more than the cost of buyingthe programmed device. By maintaining some control over distribution,the intermediaries and producers are ensured of receiving their share ofthe money for use of the material.

Readers and players for CD's and DVD's include a motor and mechanismsfor loading and unloading the storage device. The motor spins the deviceat a high rate of speed for reading the device. The motor and mechanismsinclude moving parts, which can lead to reliability problems. Inaddition, the motor and mechanisms add bulk to the readers and playersand have power requirements, which limit the suitability of CD's andDVD's for portable applications. Also, the size of the CD's and DVD'scan make transporting a number of these devices cumbersome.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a storage device. In oneembodiment, the storage device comprises a magnetic memory and a controlcircuit. The control circuit is configured to transfer selected datafrom the magnetic memory a selected number of times and to regulate thetransfer of the selected data from the magnetic memory subsequent totransferring the selected data from the magnetic memory the selectednumber of times.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are better understood with reference to thefollowing drawings. The elements of the drawings are not necessarily toscale relative to each other. Like reference numerals designatecorresponding similar parts.

FIG. 1 is a diagram illustrating an exemplary media distribution systemutilizing a storage device, according to an embodiment of the presentinvention.

FIG. 2 is a block diagram illustrating an exemplary embodiment of aread/write circuit configured to communicate with the storage device.

FIG. 3 is a block diagram illustrating an exemplary embodiment of anMRAM device used in the storage device.

FIG. 4 is a diagram illustrating an exemplary embodiment of a magneticmemory cell array section.

FIG. 5 is a diagram illustrating an exemplary embodiment of a magneticmemory cell intersected by a word line and a bit line.

FIG. 6 is a diagram illustrating an exemplary storage device, accordingto an embodiment of the present invention.

FIG. 7 is a diagram illustrating another exemplary storage device,according to an embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 is a diagram illustrating a media distribution system 40utilizing a storage device 42, according to an embodiment of the presentinvention. The distribution system 40 includes the storage device 42, aprogramming center 44, a video player 46, an audio player 48 and acomputer 50. Only a small number of exemplary components of thedistribution system 40 are shown to simplify the illustration. Inpractice, any number of suitable components can be used.

The programming center 44 downloads digital material to the storagedevice 42. The downloaded data may be any material including movies,music, books and software programs. By way of example, the downloadeddata may be a software program in which the digital material is a testfor distribution to students. The storage device 42 stores the data in amagnetic memory, such as a magnetic random access memory (MRAM), and isconfigured to transfer the data from the storage device 42 a selectednumber of times, such as at least one time. The storage device 42regulates subsequent transfers of the data from the storage device 42.In one configuration, the storage device 42 prevents a second transferof any data from the storage device 42. Regulating the transfer of datamaintains control over distribution of the digital material.

In one embodiment, the storage device 42 is a compact, card-shaped unitincluding a high density, low power MRAM. The MRAM stores the digitalmaterial for reading and playback. A control circuit coupled to the MRAMregulates the transfer of data from the MRAM and storage device 42 tothe readers and players, such as video player 46, audio player 48 andcomputer 50. The readers and players 46, 48 and 50 include communicationinterfaces for reading the storage device 42, but they do not containloading mechanisms or motors. In one configuration, the readers andplayers 46, 48 and 50 can be compact devices with low power consumption.The compact size and low power consumption of storage device 42 andreaders and players 46, 48 and 50 makes the storage device 42 suitablefor portable applications.

The programming center 44 includes a programming station 52 and acentral database 54. The programming station 52 is electrically coupledto the central database 54 through external bus 56. The central database54 contains the digital material and account information on consumerswho use the media distribution system 40. The programming station 52downloads the digital material from the central database 54 to store thematerial in storage device 42. In practice, the media distributionsystem 40 has many stations, such as programming station 52, which arein communication with the central database 54. In other embodiments, theprogramming station 44 can be in communication with local databases ofany suitable size and number.

The programming station 44 includes a display 58, a keypad 60 and a cardslot 62. The consumer uses the display 58 and keypad 60 to selectdigital material for downloading to the storage device 42. The consumeroperates the keypad 60 to scroll through menus and lists displayed onthe display 58. The card slot 62 is configured to accept the storagedevice 42 for downloading.

In operation, the consumer begins a session with the programming station52 by entering an access code. The access code is attached to an accountnumber and the consumer's account information, which is stored in thecentral database 54. The programming station 52 verifies the consumer'saccount is current and proceeds to display the next screen on display 58for selecting material to download to a storage device 42. In the eventthe consumer's account is not up to date, the transaction ends withoutdownloading material. With a current account, the consumer selectsmaterial for downloading, the storage device 42 is slid into card slot62 and the selected material is downloaded to the storage device 42.This process continues until the consumer has completed selecting anddownloading material.

A variety of readers and players, including video player 46, audioplayer 48 and computer 50, can read the storage device 42. Video player46 represents any type and size of video player including home theaterand portable applications. Video player 46 includes a playback section64 and an audio section 66. The playback section 64 and audio section 66are electrically coupled through an audio communications bus 68. Theaudio section 66 is configured to receive digital and/or analog audiosignals for playback.

The playback section 64 includes a display 70, a keypad 72 and a cardslot 74. The display 70 is electrically coupled to processing circuitryto display menus for selecting material for playback and to displayimages during playback. The keypad 72 is electrically coupled toprocessing circuitry to select menu items and material for playback. Thecard slot 74 is configured to receive the storage device 42.

In operation, the consumer begins a session with the video player 46 byinserting the storage device 42 into the card slot 74. From an initialmenu, the consumer selects a listing of material stored on the storagedevice 42. Using the keypad 72, the consumer scrolls through the listingand selects material for playback on the video player 46. The consumerinstructs the video player 46 to begin reading the storage device 42 andplaying back the selected material. The video player 46 displays videoimages on the display 70 and produces sound through the audio section66. After the selected material has been read from the storage device42, the video player 46 displays a default menu or image on the display70.

Audio player 48 represents any type and size of audio player includingdigital surround sound systems, stereo systems and portable players.Audio player 48 includes a display 76, a keypad 78 and a card slot 80.The display 76 is electrically coupled to processing circuitry todisplay menus and lists of material stored on storage device 42. Thekeypad 78 is electrically coupled to processing circuitry for scrollingthrough the menus and lists to select material for playback on the audioplayer 48. The card slot 80 is configured to receive the storage device42.

In operation, the consumer begins a session with the audio player 48 byinserting the storage device 42 into the card slot 80. Using the keypad78, the consumer directs the audio player 48 to display a listing of thematerial stored on the storage device 42. Next, the consumer selectsmaterial stored on the storage device 42 for playback. In thealternative, the consumer can direct the audio player 48 to play alllisted material stored in the storage device 42. After the audio player48 has completed reading the material from the storage device 42, theconsumer can remove the storage device 42 from the card slot 80.

The computer 50 is a portable computer and represents any type and sizeof computer. Computer 50 includes a display 82, a keypad 84, a card slot86 and speakers 88. The display 82 is electrically coupled to processingcircuitry to display menus and lists of material stored on the storagedevice 42, and to display images played back from the storage device 42.The keypad can be used to select material from the storage device 42,and the speakers 88 are electrically coupled to audio amplifiercircuitry to play sounds read from the storage device 42. The card slot86 is configured to receive the storage device 42.

In operation, the consumer begins a session with the computer 50 andinserts the storage device 42 into the card slot 86. The storage device42 is read by the computer 50 and a listing of the material stored onthe storage device 42 is displayed. The consumer uses the keypad 84 andthe display 82 to select material to be read from the storage device 42.The computer 50 reads the material and the storage device 42 is removed.

The storage device 42 is configured to transfer data a selected numberof times, such as one time. The storage device 42 regulates the transferof the data from the storage device 42 subsequent to transferring thedata the selected number of times. Regulation, as used herein, is arange of regulation from permitting the transfer of a portion of thedata subsequent to transferring the data the selected number of times,such as permitting a fixed percentage of the selected data to betransferred, to preventing the transfer of any data subsequent totransferring the data the selected number of times. In one exemplaryembodiment, the storage device 42 is configured to non-destructivelyprevent the transfer of data from the MRAM and storage device 42subsequent to transferring the data the selected number of times. Inthis embodiment, the storage device 42 is reusable and can bereprogrammed by the programming center 44. In another exemplaryembodiment, storage device 42 destructively prevents the transfer ofdata from the MRAM and storage device 42 subsequent to transferring thedata the selected number of times. In this embodiment, the storagedevice 42 may include a fuse and a fuse programming circuit electricallycoupled to a controller. The controller directs the fuse programmingcircuit to program or burn the fuse to prevent or disable the transferof data.

FIG. 2 is a block diagram illustrating an exemplary embodiment of aread/write circuit 90 configured to communicate with storage device 42.The read/write circuit 90 is configured for use in programming center44, video player 46, audio player 48 and computer 50. The read/writecircuit 90 includes a central processing unit (CPU) 92, a display 94, akeypad 96, local memory 98 and a storage device communications interface100. The display 94, keypad 96 and communications interface 100correspond to similar elements found on the programming center 44, videoplayer 46, audio player 48 and computer 50.

The CPU 92 is electrically coupled to display 94 through display bus102, and to keypad 96 through keypad bus 104. In addition, the CPU 92 iselectrically coupled to local memory 98 through memory bus 106, and toexternal bus 112. The communications interface 100 includes electricalcontacts 108 electrically coupled through the communications interface100 and interface bus 110 to CPU 92. The electrical contacts 108 areconfigured to interface with corresponding electrical contacts onstorage device 42. In the exemplary embodiment, the CPU 92 is amicroprocessor. In another embodiment, the CPU 92 can be a controllerand electrical contacts 108 can be replaced with a radio frequency (RF)interface, infrared (IR) interface or another suitable interface.

The CPU 92 is programmed to selectively perform the functions of theprogramming center 44, video player 46, audio player 48 or computer 50.The program for the CPU 92 is stored in CPU 92 and local memory 98. Thelocal memory 98 includes non-volatile memory, such as ROM, EPROM andEEPROM, and volatile memory, such as RAM. The CPU 92 reads code fromlocal memory 98 to perform functions, such as displaying menus ondisplay 94, receiving inputs from keypad 96, communicating with storagedevice 42 and communicating through external bus 112.

The CPU 92 in programming center 44 is programmed to interface with theconsumer and download digital material to the storage device 42. The CPU92 displays an initial menu on display 94 and reads inputs from keypad96 to progress through menus for accessing and downloading digitalmaterial. The CPU 92 communicates with the central database 54 throughexternal bus 112 to access account information, material lists anddownload selected material.

In operation, the consumer selects material for downloading through themenu structure and inserts storage device 42 into communicationsinterface 100 to make electrical contact with contacts 108. The CPU 92downloads the selected material from the central database 54 throughexternal bus 112. In the exemplary embodiment, the CPU 92 downloads theselected material directly to the storage device 42 throughcommunications bus 110, communications interface 100 and electricalcontacts 108. In another embodiment, the CPU 92 downloads selectedmaterial to local memory 98 and then to storage device 42. After theselected material is downloaded, CPU 92 displays a message on display 94to prompt the consumer that downloading is complete and storage device42 can be removed.

In a video player 46, audio player 48 and computer 50, the read/writecircuit 90 is configured to read storage device 42. The CPU 92 in videoplayer 46 is programmed to interface with the consumer and read orplayback digital material from storage device 42. The CPU 92 displays aninitial menu on display 94 and reads inputs from keypad 96 to progressthrough menus for selecting digital material. The consumer selectsmaterial using the keypad 96 and playback commences. The CPU 92communicates with the audio section 66 of video player 46 throughexternal bus 112.

In operation, the consumer inserts storage device 42 into communicationsinterface 100 to make electrical contact with contacts 108. Using thekeypad 96 and display 94, the consumer scans the material stored in thestorage device 42 and selects material for reading or playback. The CPU92 communicates with the storage device 42 through communicationsinterface 100 to read the selected material from storage device 42. CPU92 processes data that is read from storage device 42 to display imageson display 94 and produce sound through audio section 66. The CPU 92displays a default menu or image on display 94 after the selection hasbeen played back from storage device 42.

The CPU 92 in audio player 48 is programmed to interface with theconsumer and read or playback digital material from storage device 42.The CPU 92 displays an initial menu on display 94 and reads inputs fromkeypad 96 to progress through menus for selecting digital material. Theconsumer selects material using the keypad 96 and playback commences.The CPU 92 provides audio data through external bus 112 to an audioamplifier circuit (not shown).

In operation, the consumer inserts storage device 42 into communicationsinterface 100 to make electrical contact with contacts 108. CPU 92 readsstorage device 42 and compiles a list of material stored on storagedevice 42. The list is displayed on display 94 and the consumer scrollsthrough the list using keypad 96 to select material for playback. Aftermaterial is selected, CPU 92 reads the storage device 42 andcommunicates through external bus 112 to the audio amplifier circuit.Upon completing playback, CPU 92 displays a default menu or image ondisplay 94.

The CPU 92 in computer 50 is programmed to interface with the consumerand read or playback digital material from storage device 42. The CPU 92displays an initial menu on display 94 and reads inputs from keypad 96to progress through menus and lists for selecting digital material. Theconsumer selects material using the keypad 96 and playback commences.The CPU 92 provides audio data through external bus 112 to an audioamplifier circuit (not shown) and speakers 88.

In operation, the consumer inserts storage device 42 into communicationsinterface 100 to make electrical contact with contacts 108. The consumerselects an initial menu and CPU 92 displays the initial menu on display94. From this menu, the consumer obtains a list of material stored onstorage device 42 and selects material for use on computer 50. The CPU92 reads the selected material from the storage device 42 and providesimages and audio to display 94 and speakers 88. Upon completingplayback, CPU 92 displays a default menu or image on display 94.

The read/write circuit 90 is an exemplary embodiment of a circuit, whichcan be used to write the storage device 42 or read the storage device42. In another embodiment, the read/write circuit 90 can be configuredto both read and write the storage device 42. In this situation, thevideo player 46, audio player 48 and computer 50 can be used to programstorage device 42 as well as read storage device 42. The storage device42 regulates the transfer of data from storage device 42.

FIG. 3 is a block diagram illustrating an exemplary embodiment of anMRAM device 120 used in storage device 42. The MRAM 120 includes amagnetic memory cell array 122 electrically coupled to a write circuit124 and a read circuit (not shown for clarity). The memory cell array122 includes magnetic memory cells, indicated at 126 and describedherein.

The magnetic memory cells 126 can be of different types, for example,magnetic tunnel junction (MTJ) memory cells or giant magneto resistive(GMR) memory cells. In one configuration, magnetic memory cell 126includes a layer of magnetic film in which the orientation ofmagnetization is alterable, and a layer of magnetic film in which theorientation of magnetization may be fixed or “pinned” in a particulardirection. The magnetic film having alterable magnetization is referredto as a sense layer or data storage layer. The magnetic film that isfixed is referred to as a reference layer or pinned layer.

A memory cell 126 stores a bit of information as an orientation ofmagnetization in the sense layer. The orientation of magnetization inthe sense layer aligns along an axis of the sense layer referred to asits easy axis. Magnetic fields are applied to flip the orientation ofmagnetization in the sense layer along its easy axis to either aparallel or anti-parallel orientation with respect to the orientation ofmagnetization in the reference layer. The resistance through the memorycell 126 differs according to the parallel or anti-parallel orientationof magnetization of the sense layer and the reference layer. Thisresistance is highest when the orientation is anti-parallel, and lowestwhen the orientation is parallel. The state of the memory cell 126 canbe determined by sensing the resistance of the memory cell 126.

The memory cells 126 in array 122 are arranged in rows and columns, withthe rows extending along an x-direction and the columns extending alonga y-direction. Only a relatively small number of memory cells 126 areshown to simplify the illustration of the MRAM device 120. In practice,arrays of any suitable size can be used.

In the exemplary embodiment, the write circuit 124 includes row decoders128 a–128 b and column decoders 130 a–130 b. Row decoders 128 a–128 bare electrically coupled to word lines 132 a–132 c, and column decoders130 a–130 b are electrically coupled to bit lines 134 a–134 c. Theconductive word lines 132 a–132 c extend along the x-direction in aplane on one side of the array 122, and the conductive bit lines 134a–134 c extend along the y-direction in a plane on an opposing side ofthe array 122. There is one word line 132 for each row of the array 122,and one bit line 134 for each column of the array 122. A memory cell 126is located at each cross point of a word line 132 and a bit line 134.

During a write operation, row decoders 128 a–128 b select one of theword lines 132 a–132 c and column decoders 130 a–130 b select one of thebit lines 134 a–134 c for writing the state of the memory cell 126located at the selected word line 132 a–132 c and bit line 134 a–134 ccross point. Row decoders 128 a–128 b supply a write current through theselected word line 132 a–132 c to create a magnetic field in a selectedmemory cell 126. Row decoders 128 source the write current from rowdecoder 128 a and sink the write current in row decoder 128 b, orvice-versa. Column decoders 130 a–130 b supply a write current throughthe selected bit line 134 a–134 c to create a magnetic field in theselected memory cell 126. Column decoders 130 source the write currentfrom column decoder 130 a and sink the write current in column decoder130 b, or vice-versa. In other embodiments, the row decoders 128 a–128 band column decoders 130 a–130 b can supply current in only onedirection. In the exemplary embodiment, the write current supplied bythe write circuit 124 create magnetic fields around the selected wordline 132 a–132 c and bit line 134 a–134 c, according to the right handrule. These magnetic fields combine to set or switch the orientation ofmagnetization in the selected memory cell 126.

In one embodiment, MRAM device 120 includes sense conductors, whichextend along the x-direction in a plane on one side of the array 122.These sense conductors are electrically coupled to the read circuit forsensing the resistance of the memory cells 126. Bit lines 134 a–134 c,which extend along the y-direction on an opposing side of array 122, arealso electrically coupled to the read circuit.

During a read operation, the read circuit selects one sense conductorand one bit line 134 a–134 c to sense the resistance of the memory cell126 located at the cross point. Various methods can be used to sense theresistance. In the exemplary embodiment, a sense current is suppliedthrough the sense conductor and memory cell 126 to the bit line 134a–134 c to produce a voltage across the selected memory cell 126. Thisvoltage is detected and used to determine the state of the memory cell126. Circuits and methods for sensing the resistance and state of memorycells 126 are disclosed and described in U.S. Pat. No. 6,259,644, issuedJul. 10, 2001, entitled “Equi-potential Sense Methods for ResistiveCross Point Memory Cell Arrays”, which is incorporated herein byreference.

FIG. 4 is a diagram illustrating an exemplary embodiment of an arraysection, indicated at 140. Array section 140 includes a magnetic memorycell 126 intersected by a word line 132 a and a bit line 134 a. The wordline 132 a includes a sense conductor 143, an isolation layer 144 and awrite conductor 146. Memory cell 126 is located between bit line 134 aand sense conductor 143. Isolation layer 144 is located between senseconductor 143 and write conductor 146.

In the exemplary embodiment, write conductor 146 and bit line 134 a areelectrically coupled to write circuit 124. Write currents passed throughwrite conductor 146 and bit line 134 a create magnetic fields, accordingto the right hand rule, in memory cell 126. Sense conductor 143 and bitline 134 a are electrically coupled to the read circuit. A sense currentsupplied through sense conductor 143 and memory cell 126 to bit line 134a creates a voltage across memory cell 126. The voltage across memorycell 126 is detected over sense conductor 143 and bit line 134 a.Isolation layer 144 isolates sense conductor 143 and memory cell 126from write conductor 146 during read and write operations.

FIG. 5 is a diagram illustrating an exemplary embodiment of memory cell126 intersected by word line 132 a and bit line 134 a. Memory cell 126includes a sense layer 150, a spacer layer 152 and a reference layer154. The spacer layer 152 is located between the sense layer 150 and thereference layer 154. The sense layer 150 has an alterable magnetizationstate and the reference layer 154 has a pinned orientation ofmagnetization. The word line 132 a includes the sense conductor 143, theisolation layer 144 and the write conductor 146. The isolation layer 144is located between the sense conductor 143 and the write conductor 146.The sense conductor 143 is located next to the sense layer 150 of memorycell 126. The bit line 134 a is located next to the reference layer 154of the memory cell 126. In the exemplary embodiment, the memory cell isa spin-tunneling device where the spacer layer 152 is an insulatingbarrier layer through which an electrical charge migrates during readoperations. Electrical charge migrations through the spacer layer 152occur when a sense current is supplied through a memory cell 126. In analternative embodiment, a GMR structure can be used for memory cell 126and the spacer layer 152 is a conductor such as copper.

FIG. 6 is a diagram illustrating an exemplary storage device 42,according to an embodiment of the present invention. Storage device 42includes a controller 160, MRAM 120, an onboard memory 164, power supplycircuitry 166, an onboard communications interface 168 and onboardelectrical contacts, indicated at 170. The controller 160 iselectrically coupled to the MRAM 120 through MRAM memory bus 172. Thecontroller 160 is electrically coupled to onboard memory 164 throughonboard memory bus 174. In addition, controller 160 is electricallycoupled to communications interface 168 through communications interfacebus 176. Electrical contacts 170 are electrically coupled tocommunications interface 168 and power supply circuitry 166.

Storage device 42 is electrically coupled to a component of the mediadistribution system 40 as it is inserted into the selected component,such as programming center 44, video player 46, audio player 48 andcomputer 50. Onboard electrical contacts 170 of storage device 42electrically couple with electrical contacts 108 of read/write circuit90. This electrical coupling is a hard, physical contact between pins,such as male and female connectors.

The storage device 42 communicates with the selected component throughonboard communications interface 168 and onboard electrical contacts 170to electrical contacts 108 and communications interface 100 ofread/write circuit 90. The power supply circuitry 166 receives powerthrough the electrical contacts 170 and distributes power throughoutstorage device 42, to controller 160, MRAM 120, onboard memory 164 andcommunications interface 168. The power supply circuitry 166 includescapacitors for filtering the power and reducing the effect of noise onstorage device 42. In other embodiments, the onboard communicationsinterface 168 is a wireless or contactless interface, such as a RF or anIR interface. In these embodiments, the power supply circuitry 166 isconfigured as a wireless power supply, utilizing coupling, such ascapacitive or inductive coupling to transfer power to the storage device42.

In the exemplary embodiment, controller 160 is programmed to transferdata to and from MRAM 120. The program for controller 160 is stored incontroller 160 and onboard memory 164. The onboard memory 164 includesnon-volatile memory, such as ROM, EPROM and EEPROM, and volatile memory,such as RAM. The controller 160 reads operating code from thenon-volatile memory and uses the volatile memory for temporary storageand a scratch pad.

The MRAM 120 is the high density, low power magnetic memory previouslydescribed in this specification. The MRAM 120 is capable of storing alarge quantity of data and in storage device 42, MRAM 120 stores thedigital material selected and downloaded through programming center 44.In the exemplary embodiment, the controller 160, MRAM 120, onboardmemory 164 and communications interface 168, are separate integratedcircuits and devices electrically coupled to a circuit board. In anotherembodiment, the controller 160, MRAM 120, onboard memory 164 andcommunications interface 168 are combined into an application specificintegrated circuit (ASIC).

The controller 160 is programmed to transfer material from theprogramming center 44 and store the material in the MRAM 120. For eachitem of material stored in MRAM 120, the controller 160 stores an itemof material identifier in an index that is stored in non-volatile memoryof onboard memory 164. Each item of material identifier, referred to asan index entry, includes the title, the address in MRAM 120 where thematerial is stored and the byte count of the item. The byte count isreferred to as a data count of the item stored in MRAM 120. In otherembodiments, the data count is the number of 16-bit or 32-bit portionsof data, such that the data count is not limited to an 8-bit byte count.

The readers and players 46, 48 and 50 read the index through thecontroller 160 to produce a list of items stored in the storage device42. In a reusable storage device 42, the index is updated each time thestorage device 42 is programmed with new material. Old index entries areover-written, as is the old material in MRAM 120.

During playback or reading of an item of material from MRAM 120, thecontroller 160 counts the number of bytes transferred, referred to as atransfer count, for the selected item of material. The controller 160compares the transfer count and the data count taken from the indexentry for the item of material to obtain a compare result. If thecompare operation results in the transfer count exceeding the datacount, the controller 160 sets a bit in the index entry for the selecteditem of material to indicate 100 percent or more of the item has beentransferred. The storage device 42 regulates subsequent transfer of theselected item in response to the bit being set. The bit indicates astate indicative of the amount of data transferred from the MRAM 120 forthe selected item.

In other embodiments, more complicated schemes can be devised toindicate the amount of data transferred from the MRAM 120. In oneembodiment, the controller 160 can store a running percentage indicativeof the amount of data transferred from the MRAM 120 for a selected item.The controller 160 can be programmed to disable or prevent the transferof data from the MRAM 120 after a percentage, such as 120 percent or 150percent of the data for a selected item has been read from the storagedevice 42. Responding to a higher percentage allows for replaying orrereading certain portions of the selected item of material.

In the exemplary embodiment, the controller 160 sets a bit to indicatethe state that 100 percent or more of the data for a selected item hasbeen read from the MRAM 120 and storage device 42. In response to thetransfer count exceeding the data count, the controller 160 prevents theselected item of material from being transferred out of MRAM 120 andstorage device 42. The controller 160 is configured to disable orprevent the transfer of data non-destructively. By non-destructivelydisabling the transfer of data, the storage device 42 can be used forreading other items of material and loading new items into the storagedevice 42.

In one configuration, the controller 160 is programmed to stoptransferring data and erase the index entry of the selected item afterthe transfer count for the item has exceeded the data count. In thiscase, the index entry is over-written with all ones or all zeros or acheckerboard pattern to erase it. The erased index entry item identifierno longer shows up in any lists on the readers and players 46, 48 and50. In this situation, the storage device 42 is reusable. The old indexentry, which was erased, is over-written when new material is loadedinto the storage device 42.

In another configuration, the controller 160 is programmed to stoptransferring data and erase some or all of the data for the item ofmaterial from MRAM 120 in response to the transfer count exceeding thedata count. In this situation, the index entry is also erased toeliminate the title of the material from any listing and to avoidconfusion. The MRAM 120 is over-written with ones or zeros or acheckerboard pattern to erase the data from MRAM 120. Erasing the datafrom MRAM 120 increases the control maintained over distribution of thematerial. Once the data is erased from MRAM 120, it cannot be easilyrecovered. The storage device 42 is still reusable such that the indexentry and MRAM 120 can be over-written with new data.

In another configuration, the controller 160 is programmed to stop thetransfer of data and signal the communications interface 168 to disableinput/output circuitry. In this configuration, the controller 160disables one or more inputs and/or one or more outputs. The storagedevice 42 is configured to receive some signals from the readers andplayers 46, 48 and 50, such that the consumer can call up the list ofmaterial from the storage device 42 and select a different item tocontinue. In this configuration, the controller 160 reads the indexentry for a selected item and determines if the bit is set. If the bitis not set, the controller 160 proceeds to transfer data from MRAM 120and out of storage device 42. If the bit is set, the controller 160transmits an error message to the reader and player 46, 48 and 50.

Each of the above configurations includes non-destructive disabling ofthe transfer of data from MRAM 120 and storage device 42 to readers andplayers 46, 48 and 50. In these configurations, the power supply circuit166 includes enough capacitance to power the storage device 42 while thecontroller 160 is setting bits and erasing information, which helps toprevent people from removing the device 42 before a bit can be set or anindex entry erased.

FIG. 7 is a diagram illustrating another exemplary storage device 142,according to an embodiment of the present invention. The storage device142 includes controller 160, MRAM 120, onboard memory 164, powercircuitry 166, onboard communications interface 168 and onboardelectrical contacts 170. In addition, storage device 142 includes a fuseprogramming circuit 180 and a fuse circuit 182. The fuse circuit 182 iselectrically coupled between the controller 160 and the communicationsinterface 168, including input/output circuitry. The fuse circuit 182 iselectrically coupled to the controller 160 through fuse bus 184. Thefuse circuit 182 is electrically coupled to the communications interface168 through input/output bus 186. The fuse programming circuit 180 iselectrically coupled to the controller 160 through programming controlline 188, and the fuse programming circuit 180 is electrically coupledto the fuse circuit 182 for programming or burning the fuse circuit 182through fuse programming line 190. The controller 160 is electricallycoupled to MRAM 120 through MRAM bus 172, and to onboard memory 164through onboard memory bus 174. In another embodiment, the fuse circuit182 is electrically coupled between the MRAM 120 and controller 160. Inthis configuration, the MRAM bus 172 is split into two parts and thefuse circuit 182 is inserted between and electrically coupled to the twoparts.

In this exemplary embodiment, the controller 160 maintains the index ofitems of material stored in MRAM 120. As described above, the index isstored in non-volatile memory in the onboard memory 164. Each indexentry includes the data count of the item stored in MRAM 120. Thecontroller 160 keeps a transfer count corresponding to the number ofbytes of data transferred out of the storage device 42 for a selecteditem. The controller 160 compares the transfer count for a selected itemto the data count of that item to obtain a compare result. Thecontroller 160 disables transfer of data in response to the transfercount exceeding the data count.

In the exemplary embodiment, the storage device 142 destructivelydisables transfer of data from MRAM 120 and storage device 142. Thecontroller 160 is programmed to signal the fuse programming circuit 180to program, i.e. burn, one or more fuses in the fuse circuit 182. Thefuse circuit 182 is a bus circuit including at least one fuse in serieswith bus lines, which lead from controller 160 to communicationsinterface 168. In the exemplary embodiment, one or more bus lines have afuse in series and the fuse programming circuit 180 burns the fuses opento disable the transfer of data from MRAM 120 and storage device 142 toreaders and players 46, 48 and 50. Burning the fuses destructivelydisables the transfer of data. The storage device 142 cannot be reused,short of replacing the fuse circuit 182. Destructively disabling thestorage device 142 raises the level of control maintained overdownloaded material. To raise the level further, the controller 160 isprogrammed to erase index entries and the MRAM 120. In the exemplaryembodiment, the fuse circuit 182 can be replaced and the storage device142 can be reused. However, with the index entries and MRAM 120 erased,a high level of control is maintained over the distribution of materialdownloaded to the storage device 42.

In another embodiment, the fuse circuit 182 is electrically coupledbetween the controller 160 and MRAM 120. The MRAM bus 172 is dividedinto two parts and the fuse circuit 182 is electrically coupled betweenthe two parts. In this embodiment, the transfer of data is destructivelydisabled between MRAM 120 and controller 160. To erase MRAM 120, thecontroller 160 burns the fuse circuitry 182 after MRAM 120 is erased.Index entries are erased at will.

The storage devices 42 and 142 are compact, card-shaped units includinghigh density, low power MRAM 120. The small size of the storage devices42 and 142 makes them easy to carry. In addition, the reduced powerconsumption of the readers and players 46, 48 and 50 make the storagedevices 42 and 142 suitable for portable applications. The storagedevices 42 and 142 maintain control over the distribution of downloadedmaterial by disabling and preventing the transfer of the same data twicefrom MRAM 120. Also, the electronic transfer of data is less cumbersomeand burdensome on the consumer as compared to renting CD's and DVD's.

1. A storage device, comprising: a magnetic memory; and a controlcircuit configured to transfer selected data from the magnetic memory aselected number of times and to regulate the transfer of the selecteddata from the magnetic memory subsequent to transferring the selecteddata from the magnetic memory the selected number of times, wherein thecontrol circuit is configured to stop the transfer of the selected datasubsequent to transferring the selected data from the magnetic memorythe selected number of times.
 2. The storage device of claim 1, whereinthe selected number of times that the control circuit is configured totransfer the selected data is once.
 3. The storage device of claim 1,wherein the selected number of times that the control circuit isconfigured to transfer the selected data is a fraction greater than one.4. The storage device of claim 1, wherein the control circuit isconfigured to erase at least some of the selected data from the magneticmemory to regulate the transfer of the selected data from the magneticmemory.
 5. The storage device of claim 1, wherein the control circuit isconfigured to erase an index entry for the selected data to regulate thetransfer of the selected data from the magnetic memory.
 6. The storagedevice of claim 1, wherein the control circuit is configured to disablean input/output circuit to regulate the transfer of the selected datafrom the magnetic memory.
 7. The storage device of claim 1, wherein thecontrol circuit comprises a fuse configured to be programmed to regulatethe transfer of the selected data from the magnetic memory.
 8. Thestorage device of claim 1, wherein the control circuit comprises acontroller programmed to transfer the selected data from the magneticmemory the selected number of times and to regulate the transfer of theselected data from the magnetic memory subsequent to transferring theselected data from the magnetic memory the selected number of times. 9.The storage device of claim 1, wherein the control circuit is configuredto store a data count of the selected data.
 10. The storage device ofclaim 9, wherein the control circuit is configured to obtain a transfercount of the selected data transferred from the magnetic memory, tocompare the transfer count to the data count of the selected data toobtain a compare result and to regulate the transfer of the selecteddata from the magnetic memory in response to the compare result.
 11. Thestorage device of claim 1, wherein the control circuit is configured toprogram a state into non-volatile memory indicative of an amount of theselected data transferred from the magnetic memory.
 12. The storagedevice of claim 11, wherein the control circuit is configured to readthe state from the non-volatile memory and to regulate the transfer ofthe selected data from the magnetic memory based on the state read fromthe non-volatile memory.
 13. The storage device of claim 11, comprisinginput/output circuitry electrically coupled to the control circuit,wherein the control circuit is configured to read the state from thenon-volatile memory and to disable the input/output circuitry based onthe state read from the non-volatile memory.
 14. A storage device,comprising: a magnetic memory; and a controller electrically coupled tothe magnetic memory, wherein the controller is configured to read datafrom the magnetic memory during a first transfer of the data from themagnetic memory and to prevent reading of the data from the magneticmemory after the first transfer of the data from the magnetic memory.15. The storage device of claim 14, wherein the controller is configuredto erase at least some of the data from the magnetic memory to preventreading of the data from the magnetic memory after the first transfer ofthe data from the magnetic memory.
 16. The storage device of claim 14,wherein the controller is configured to store a data count of the data,to obtain a transfer count of the data as the data is transferred fromthe magnetic memory in the first transfer and to erase at least some ofthe data from the magnetic memory in response to the transfer countexceeding the data count after the first transfer of the data from themagnetic memory.
 17. The storage device of claim 14, comprising: a fuseconnected to the controller; and a programming circuit electricallycoupled to the fuse and the controller, wherein the controller isconfigured to signal the programming circuit to cause the fuse todisable reading of the data from the magnetic memory after the firsttransfer of the data from the magnetic memory.
 18. The storage device ofclaim 14, comprising: a fuse electrically coupled to the controller andthe magnetic memory; and a programming circuit electrically coupled tothe fuse and the controller, wherein the controller is configured tosignal the programming circuit to cause the fuse to disable reading ofthe data from the magnetic memory after the first transfer of the datafrom the magnetic memory.
 19. The storage device of claim 14,comprising: an input/output circuit; a fuse electrically coupled to thecontroller and the input/output circuit; and a programming circuitelectrically coupled to the fuse and the controller, wherein thecontroller is configured to signal the programming circuit to cause thefuse to disable reading of the data from the magnetic memory after thefirst transfer of the data from the magnetic memory.
 20. The storagedevice of claim 14, wherein the controller programs a state intonon-volatile memory to indicate an amount of the data has beentransferred from the magnetic memory during the first transfer of thedata from the magnetic memory.
 21. The storage device of claim 20,wherein the controller is configured to read the state from thenon-volatile memory and to prevent reading of the data from the magneticmemory based on the state read from the non-volatile memory.
 22. Thestorage device of claim 20, comprising input/output circuitryelectrically coupled to the controller, wherein the controller isconfigured to read the state from the non-volatile memory and to preventreading of the data by disabling the input/output circuitry based on thestate read from the non-volatile memory.
 23. A method of controllingmaterial distribution from a magnetic memory, comprising: transferringselected data from the magnetic memory a selected number of times;regulating the transfer of the selected data from the magnetic memorysubsequent to transferring the selected data from the magnetic memorythe selected number of times; and stopping the transfer of the selecteddata subsequent to transferring the selected data from the magneticmemory the selected number of times.
 24. A method of controllingmaterial distribution from a magnetic memory, comprising: transferringselected data from the magnetic memory a selected number of times; andregulating the transfer of the selected data from the magnetic memorysubsequent to transferring the selected data from the magnetic memorythe selected number of times, wherein regulating the transfer comprisesone from a group comprising: erasing some of the selected data from themagnetic memory; erasing an index entry corresponding to the selecteddata; disabling an input/output circuit during attempts to transfer theselected data; and programming a fuse to disable the transfer of theselected data from the magnetic memory.
 25. A method of controllingmaterial distribution from a magnetic memory, comprising: transferringselected data from the magnetic memory a selected number of times; andregulating the transfer of the selected data from the magnetic memorysubsequent to transferring the selected data from the magnetic memorythe selected number of times, wherein regulating the transfer comprises:storing a data count of the selected data; obtaining a transfer count ofthe selected data transferred from the magnetic memory; comparing thetransfer count and the data count to obtain a compare result; andregulating the transfer of the selected data from the magnetic memorybased on the compare result.
 26. A method of controlling materialdistribution from a magnetic memory, comprising: transferring selecteddata from the magnetic memory a selected number of times; regulating thetransfer of the selected data from the magnetic memory subsequent totransferring the selected data from the magnetic memory the selectednumber of times; and programming a state into non-volatile memory toindicate an amount of the selected data transferred from the magneticmemory.
 27. The method of claim 26, wherein regulating the transfercomprises: reading the state from the non-volatile memory; andregulating the transfer of the data from the magnetic memory based onthe state read from the non-volatile memory.
 28. The method of claim 26,wherein regulating the transfer comprises: reading the state from thenon-volatile memory; and disabling input/output circuitry based on thestate read from the non-volatile memory.